I recently fixed my steering wheel radio controls on my Formula based on a writeup I had seen a long time ago that seems to not exist anymore.
It seems like a common problem on the older cars.

Hope this helps anyone whose controls don't work....

First, remove the airbag and horn fuses from the interior fuse panel.
Otherwise the horn will come on and stay on once you start removing the airbag.
Then, remove the four screws from the back of the steering wheel, one at each corner of the airbag. They are the annoying little five star head screws.

Once you get the airbag loose, you'll need to disconnect the airbag ground, the wire that goes to the radio, and the airbag sensor wire.

Then, you can remove the airbag+controls from the car and work on it somewhere more convenient than the driver's seat.

Remove the controls from the airbag(more annoying smaller five stars) and then take the controls apart (you'll need a small 1/4 drive socket to do this).

Once you have the actual buttons apart, you can look at the assembly, and see whats causing the problem. Its a circuit board underneath the buttons, and the buttons push on little rubber actuators which contact the circuit board. Over time these little rubber things had reached the consistency of chewed bubble gum in my car, so no matter how hard you pushed the button it wasnt going to work.

Take the buttons off of their mounts (be careful not to lose any of the little springs underneath them). What you'll need now is a couple of the little red spray tubes that come with a can of WD-40. You'll need to cut these into about 1/8 inch pieces IIRC. Make sure you remove all the gummy stuff from inside the buttons, replace it with a piece of spray tube, reassemble in reverse order, replace fuses and you're good to go!

My buttons have a nice quality feel now, and they operate really easily. I never use the head unit controls anymore, its just too convenient to have em on the steering wheel.

Thanks to whoever came up with this fix originally, it helped me out a lot.